JP2017152129A - Thin battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin battery in which a crack hardly occurs in an outer package at a stepped portion where the thickness of an electrode group varies, and spreading of a convex shape hardly occurs.SOLUTION: A thin battery includes an electrode group 103, nonaqueous electrolyte, and an exterior body 108 for hermetically housing them. The electrode group 103 includes a first electrode, a second electrode, and a separator. The first electrode includes a first current collector sheet and a first active material layer. The second electrode includes a second current collector sheet and a second active material layer. The first current collector sheet and the second current collector sheet contain tabs 114 and 124 which respectively extend in a first direction and are connected to leads 113 and 123. The exterior body 108 has a sealing margin for sandwiching the leads 113, 123, a first site facing the active material layer, and a second site between the first site and the sealing margin. The first site has a flat surface or has a plurality of first linear convex portions 108a intersecting with the first direction, and the second site has a second linear convex portion 108b which intersects with the first direction and is higher in height than the first linear convex portion 108a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thin battery including a sheet-like electrode group.

  In recent years, as a power source for small electronic devices such as bio-applied devices, mobile phones, audio recording / playback devices, watches, video and still image cameras, liquid crystal displays, calculators, IC cards, temperature sensors, hearing aids, pressure-sensitive buzzers, etc. Thin batteries are used. Such a thin battery is required to have flexibility. For example, a thin battery mounted on a biological sticking type device or a wearable portable terminal is required to be deformed so as to follow the movement of the living body. Therefore, it has been proposed to provide corrugated irregularities on the exterior body so that the exterior body is easily contracted inside the bent portion and easily stretched outside (Patent Documents 1 and 2).

International Publication No. 2012/140709 Pamphlet JP2015-130332A

  The inside of the exterior body of the thin battery is decompressed in a state in which the electrode group and the nonaqueous electrolyte are accommodated. Therefore, the appearance of the thin battery tends to be uneven according to the stepped portion where the thickness of the electrode group changes. In the step portion where the thickness of the electrode group changes, when the thin battery is bent, a crack is likely to occur or a convex bulge is likely to occur.

  In view of the above, one aspect of the present invention includes a sheet-like electrode group, a nonaqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the nonaqueous electrolyte, The electrode group includes a sheet-like first electrode, a sheet-like second electrode, and a separator disposed between the first electrode and the second electrode, wherein the first electrode is The first current collector sheet includes a first active material layer attached to the first current collector sheet and the first current collector sheet, and the second electrode is a second current attached to the second current collector sheet and the second current collector sheet. An active material layer, and the first current collector sheet includes a first tab extending in a first direction from a part of one side of the first current collector sheet, and the first tab includes a first tab of the exterior body. A first lead drawn out is connected, and the second current collector sheet is connected to the second current collector sheet. A second tab extending in a first direction from a part of the side, and a second lead drawn out of the exterior body is connected to the second tab, and the exterior body includes the first lead And a sealing margin for sandwiching the second lead, and the exterior body includes a first portion facing the first active material layer and the second active material layer, the first portion, and the sealing margin. A second portion between the first portion, the first portion has a flat surface, or a plurality of striped first linear protrusions intersecting the first direction, and the second portion The present invention relates to a thin battery in which a portion has at least one second linear convex portion intersecting with the first direction, and the height of the second linear convex portion is larger than the height of the first linear convex portion.

  According to the present invention, when a thin battery is bent, cracks are unlikely to occur at a step portion where the thickness of the electrode group changes, and a convex bulge is less likely to occur.

It is the top view which notched a part of the exterior body of the thin battery which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the principal part of the thin battery. It is a figure which shows the positional relationship of the 1st linear convex part in the thickness direction of an electrode group, and a 2nd linear convex part. It is a longitudinal cross-sectional view of the principal part of the thin battery which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view of the principal part of the thin battery which concerns on 3rd Embodiment.

  A thin battery according to an embodiment of the present invention includes a sheet-like electrode group, a nonaqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the nonaqueous electrolyte. The electrode group includes a sheet-like first electrode, a sheet-like second electrode, and a separator disposed between the first electrode and the second electrode. The first electrode includes a first current collector sheet and a first active material layer attached to the first current collector sheet. The second electrode includes a second current collector sheet and a second active material layer attached to the second current collector sheet. The first current collector sheet has a first tab extending in a first direction from a part of one side of the first current collector sheet, and the second current collector sheet is one side of the second current collector sheet. A second tab extending in a first direction from a portion of the first tab.

  A first lead drawn out of the exterior body is connected to the first tab, and a second lead drawn out of the exterior body is connected to the second tab. It has a sealing margin for sandwiching the lead and the second lead.

  Note that the sealing allowance of the outer package is, for example, when the outer package is formed by bonding the peripheral portions of two film materials, or the peripheral portions other than the folds are bonded by folding one film material. The peripheral part when forming an exterior body. For example, if the outer shape of the exterior body is a rectangle or a shape close to a rectangle, the peripheral edge along one of the four sides serves as a sealing margin for sandwiching the first lead and the second lead.

  The exterior body has a first part facing the first active material layer and the second active material layer, and a second part between the first part and the sealing allowance. The second part is usually a region of the first current collector sheet that does not have the first active material layer and a region of the second current collector sheet that does not have the second active material layer (particularly the first tab and the second Tab) and at least part of the first lead and at least part of the second lead.

  Here, the first portion has a flat surface or a plurality of striped first linear convex portions intersecting with the first direction. The second part has at least one second linear protrusion intersecting with the first direction. The first part may not have a plurality of first linear protrusions. However, when the first part has a plurality of first linear protrusions, the height of the second linear protrusions is made larger than the height of the first linear protrusions. In addition, when two or more 2nd linear convex parts are provided in the 2nd site | part, the height of at least 1 2nd linear convex part is higher than the height of the 1st linear convex part with the largest height. It only needs to be large.

  The linear protrusion has an elongated ridge or a shape like a rib or a ridge. When a plurality of linear convex portions are provided, a concave portion is formed between adjacent linear convex portions. The recess has a shape like an elongated recess or a groove. The plurality of linear convex portions provided in stripes always include a concave portion, and the cross section exhibits a waveform. Therefore, the cross section of the several 1st linear convex part provided in stripe form is a waveform. It is sufficient that at least one second linear convex portion exists, but a plurality of second linear convex portions may be provided in a striped manner so that the cross-section is corrugated like the first linear convex portion. . It is desirable that the heights of the plurality of first linear protrusions are substantially uniform, and the average (m1) and standard deviation (σ1) of all the first linear protrusions is 0.9 ≦ (m1−σ1). ) / M1 is desirable. Similarly, it is desirable that the heights of the plurality of second linear protrusions are substantially uniform, and the average (m2) and standard deviation (σ2) of all the second linear protrusions is 0.9 ≦ ( It is desirable to satisfy m2-σ2) / m2.

  A thin battery usually has a step corresponding to a change in the thickness of the electrode group at the boundary between the first part and the second part. At the boundary between the first part and the second part, inevitable deformation occurs in the exterior body. When the second linear convex portion is not provided in the second portion, when the thin battery is bent, a defect such as a crack or a bulge often occurs starting from the deformed portion. On the other hand, when the second linear convex portion is provided at the second portion, the stress when the thin battery is bent increases the width of the concave portion between the second linear convex portion or the adjacent second linear convex portions. Or it can be alleviated by shrinking. Thus, cracks and swelling problems are less likely to occur.

  Both the first linear convex portion and the second linear convex portion are formed so as to cross the first direction. When the direction in which the first linear convex portion and the second linear convex portion extend is the second direction, the angle formed by the first direction and the second direction is preferably 80 to 100 degrees (°), and is 90 degrees. More preferably. Thereby, when a thin battery bends along the first direction, it becomes easier to bend. In addition, cracks are less likely to occur at the step portions where the thickness of the electrode group changes, and convex bulges are less likely to occur.

  Since the first portion of each electrode facing the active material layer is stuck to the electrode group by reducing the pressure inside the outer package, it is difficult to cause defects such as cracks and swelling. Therefore, the 1st part does not need to have a plurality of 1st line convex parts provided in stripes. In the case where the first portion has a flat surface, the flat surface may be substantially flat, and slight unevenness may exist. However, in order to say that it is a flat surface, the level | step difference which such an unevenness | corrugation has is desirably 10 μm or less and more desirably 5 μm or less. Although it is not necessary for the entire surface of the first part to be flat, when the entire surface of the first part is flat, it is easy to manufacture a thin battery.

  In the case where the first portion has a plurality of striped first linear protrusions, the second line is higher than the height of the first linear protrusions in order to suppress defects such as cracks and swelling when the thin battery is bent. It is desirable to increase the height of the convex portion so that the unevenness of the second part is preferentially involved in stress relaxation. Thereby, not only can the above-mentioned problem be suppressed, but also the thickness of the battery can be avoided from being excessively increased by the first linear protrusions. It is desirable that the height of the first linear protrusion is as small as possible.

  The heights of the first linear protrusion and the second linear protrusion correspond to the amplitude of the sine wave when the cross-sectional shape when the linear protrusion is viewed from the second direction is regarded as a sine wave. That is, the height of the linear convex portion corresponds to a difference in height between the bottom of the adjacent concave portion (surface on the battery inner surface side of the outer package) and the top of the convex portion (surface on the outer surface of the outer battery body). When the level of the bottom of the two concave portions adjacent to the linear convex portion is different, the height difference between the bottom of each concave portion and the top of the convex portion is obtained, and the height of the linear convex portion is obtained as an average value of the two values. What is necessary is just to ask for it.

  In a preferred embodiment, the center point of the height of the second linear protrusion is located closer to the center than the outermost part of the first part in the thickness direction of the electrode group. Thereby, a 2nd linear convex part does not protrude excessively, and it becomes easy to mount a thin battery in a use apparatus. Further, even when the top of the second linear protrusion protrudes beyond the outermost part of the first part, the degree of protrusion is small, and the second linear protrusion has flexibility, so that it is mounted on the device used. It is hard to be a hindrance. In addition, when two or more 2nd linear convex parts are provided, the center point of the highest 2nd linear convex part should just be located in the center rather than the outermost part of a 1st site | part. .

  Here, the center point of the height of the second linear convex portion is a point located at half the height from the bottom of the concave portion adjacent to the second linear convex portion to the top of the convex portion. . If the levels of the bottoms of two adjacent recesses are different, find a point located at half the height from the bottom of each recess to the top of the projection, and center the midpoint between the two points As long as you ask.

  The outermost part of the first part is a surface on the outer surface side of the exterior body constituting the first part, and is the part farthest from the center in the thickness direction of the electrode group. When the first part has the first linear convex part, the top of the highest first linear convex part is the outermost part of the first part. In addition, when the first part does not have the first linear protrusion and is flat, usually, any point on the outer surface side of the exterior body constituting the first part is the outermost part of the first part. It is.

  In a more preferred embodiment, the top of the second linear convex portion is located closer to the center than the outermost portion of the first portion in the thickness direction of the electrode group. Thereby, the 2nd linear convex part does not protrude from the principal part of a thin battery, and it becomes easier to mount a thin battery in a use apparatus. In addition, when two or more 2nd linear convex parts are provided, the top part of the highest 2nd linear convex part should just be located near the center rather than the outermost part of a 1st site | part.

  The thickness of the thin battery is not particularly limited, but considering flexibility, it is preferably 3 mm or less, more preferably 2 mm or less, or 1.5 mm or less. The lower limit of the thickness of the thin battery is, for example, 50 μm.

  When at least a part of the non-aqueous electrolyte forms a gel electrolyte, the gel electrolyte can adhere the first active material layer and the separator and the second active material layer and the separator. it can. Thereby, although the bending performance of an electrode group is improved, on the other hand, when a battery is greatly bent, the load applied to an exterior body tends to increase. In such a case, the 2nd linear convex part provided in the 2nd site | part demonstrates the remarkable effect which relieve | moderates the load concerning an exterior body.

  A battery-mounted device according to an embodiment of the present invention includes the thin battery and a flexible electronic device driven by power supply from the thin battery, and the thin battery and the electronic device are integrated into a sheet. It has become. Electronic devices that are integrated into a sheet with a thin battery include, for example, a bio-applied device or a wearable mobile terminal, a mobile phone, a voice recording / playback device, a wristwatch, a video and still image camera, a liquid crystal display, Calculators, IC cards, temperature sensors, hearing aids, pressure-sensitive buzzers, etc. In particular, the bio-applied device is required to be flexible because it is used in close contact with a living body. Examples of the biological sticking type device include a biological information measuring device and an iontophoresis transdermal dosage device.

  The thickness of the sheet-like battery-mounted device may be thicker than that of the thin battery, but is preferably 5 mm or less, and more preferably 3 mm or less. If the thickness of the battery-mounted device is about 5 mm or less, relatively good flexibility can be obtained. The lower limit of the thickness of the battery-mounted device is, for example, 50 μm.

Although the structure of an electrode group is not specifically limited, For example, the following can be mentioned.
The electrode group having the simplest structure includes one first electrode, one second electrode, and a separator interposed between the first electrode and the second electrode. In this case, the first electrode may be a single-sided electrode including the first current collector sheet and the first active material layer attached to one surface thereof. The second electrode may also be a single-sided electrode including a second current collector sheet and a second active material layer attached to one surface thereof.

  Next, the electrode group having a simple structure has a three-layer structure including one first electrode and two second electrodes sandwiching the first electrode. Such a thin battery has a small thickness and a sufficiently practical capacity. In this case, the second electrode may be a single-sided electrode including the second current collector sheet and the second active material layer attached to one surface thereof. On the other hand, the first electrode may be a double-sided electrode including a first current collector sheet and a first active material layer attached to both surfaces.

  The electrode group having another structure includes, for example, two or more first electrodes and three or more second electrodes, and the first electrodes and the second electrodes are alternately stacked. Among such electrode groups, the simplest structure has two first electrodes, one second electrode interposed between the two first electrodes, and one each outside the two first electrodes. And a second electrode disposed. Such a thin battery has not only a small thickness but also a high capacity. In this case, the first electrode may be a double-sided electrode including a first current collector sheet and a first active material layer attached to both surfaces. One second electrode interposed between the two first electrodes may also be a double-sided electrode including a second current collector sheet and a second active material layer attached to both surfaces thereof. On the other hand, the second electrodes arranged on the outermost sides may be single-sided electrodes including a second current collector sheet and a second active material layer attached to one surface thereof.

  Hereinafter, embodiments of the present invention will be described in more detail. However, the following embodiments do not limit the scope of the invention.

(First embodiment)
Next, the thin battery according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view in which a part of an outer package of a thin battery is cut out, and FIG. 2 is a longitudinal sectional view showing a main part of the thin battery. 2 corresponds to a cross-sectional view taken along the line II-II of the thin battery shown in FIG.

  The thin battery 100 includes an electrode group 103, a nonaqueous electrolyte (not shown), and an exterior body 108 that houses these. The electrode group 103 includes one first electrode 110 and a pair of second electrodes 120 that sandwich the first electrode 110, and a separator 107 is interposed between the first electrode 110 and the second electrode 120. Yes. The first electrode 110 includes a first current collector sheet 111 and a first active material layer 112 attached to both surfaces. The second electrode 120 includes a second current collector sheet 121 and a second active material layer 122 attached to one surface thereof.

  The first current collector sheet 111 has a first tab 114 extending from one side thereof. A first lead 113 is connected to the first tab 114, and the first lead 113 is drawn out of the exterior body 108.

  Similarly, the second current collector sheet 121 has a second tab 124 extending from one side thereof. The second tabs 124 of the pair of second current collector sheets 121 are overlapped with each other and electrically connected by, for example, welding. Thereby, the collective tab 124A is formed. A second lead 123 is connected to the assembly tab 124 </ b> A, and the second lead 123 is drawn out of the exterior body 108.

  End portions of the first lead 113 and the second lead 123 led out of the exterior body 108 function as a first external terminal or a second external terminal, respectively. It is desirable to interpose a sealing material 130 between the exterior body 108 and each lead in order to improve hermeticity. For the sealing material 130, a thermoplastic resin having a heat welding property can be used.

  In FIG. 1, the electrode group 103 is generally rectangular, but the shape of the electrode group 103 is not limited to this. The shape of the electrode excluding the tab may be a shape having a straight portion from which the tab protrudes, and is rectangular (including a square), trapezoid, parallelogram, substantially elliptical shape having a straight portion in part, at least one round Examples include a substantially rectangular shape having a corner, a substantially trapezoidal shape, and a substantially parallelogram shape. From the viewpoint of productivity, a rectangular shape or a substantially rectangular shape is preferable. When the electrode group is rectangular or substantially rectangular, the ratio of the length of the long side to the short side is, for example, long side: short side = 1: 1 to 8: 1. Usually, the direction along the long side is the first direction in which the tab extends.

  The shape of the tab is not particularly limited. The shape of the tab is, for example, a rectangle (including a square), a trapezoid, a parallelogram, a semicircle, a semi-ellipse, a rectangle with an arc at the tip, a substantially rectangle having at least one round corner, a substantially trapezoid, and a substantially parallelogram. Such as shape.

  As shown in FIG. 2, the exterior body 108 includes a first part 108 </ b> A that faces the first active material layer 112 and the second active material layer 122, and the first active material layer 112 of the first current collector sheet 111. A region not having the second active material layer 122 (particularly the second tab 124) and the second lead 123 of the second non-active region (particularly the first tab 114) and a part of the first lead 113 and the second current collector sheet 121. It can be divided into a second part 108B facing a part of the second part 108B.

  The connection position between each tab and each lead is not limited to the illustrated example. For example, the connection position between each tab and each lead may be closer to the end of each active material layer. That is, you may make most area | regions of the 2nd site | part of an exterior body oppose a 1st lead and a 2nd lead. In this case, the opposing region between the first tab and the second tab and the second portion may be smaller.

  In the illustrated example, the first portion 108A has a plurality of first linear protrusions 108a provided in a stripe shape so as to intersect perpendicularly with the first direction. The second portion 108B has a plurality of second linear protrusions 108b provided in a stripe shape so as to intersect perpendicularly with the first direction. The height of the second linear protrusion 108b is formed larger than the height of the first linear protrusion 108a.

  When the thin battery 100 is bent, the width of the concave portion between the second linear convex portion 108b or the adjacent second linear convex portion 108b is enlarged or reduced in preference to the first linear convex portion 108a. The first linear protrusion 108a is considered to work in the same manner, but it is considered that the first portion 108A is relatively firmly attached to the electrode group 103, and thus is unlikely to contribute to stress relaxation of the exterior body. It is sufficient that at least one second linear protrusion 108b is formed. However, from the viewpoint of enhancing the effect of suppressing cracking of the exterior body 108 and the swelling of the convex shape at the stepped portion of the electrode group 103, two or more, further three or more second linear convex portions 108b are formed. Is desirable.

FIG. 3 is a diagram conceptually extracting only the exterior body 108 depicted in FIG. 2, and the positions of the first linear protrusions 108 a and the second linear protrusions 108 b in the thickness direction of the electrode group 103. Showing the relationship.
In FIG. 3, the line La indicates the level of the outermost portion of the first portion 108 </ b> A, that is, the top of the highest first linear protrusion 108 a (max) (the surface on the battery outer surface side of the exterior body). Line Lb indicates the level of the bottom of the recess (surface on the battery inner surface side of the exterior body) adjacent to the first linear protrusion 108a (max). In the illustrated example, the height difference (interval) ha between the line La and the line Lb is substantially the same, and the height difference ha corresponds to the height of the first linear protrusion 108a (max).

  In FIG. 3, line LA indicates the level of the top (surface on the battery outer surface side of the outer package) of the highest second linear protrusion 108 b (max) formed in the second portion 108 </ b> B. Line LB indicates the level of the bottom of the concave portion adjacent to the second linear convex portion 108b (max) (the surface on the battery inner surface side of the exterior body). In the illustrated example, the height difference (interval) hb between the line LA and the line LB is substantially the same, and the height difference hb corresponds to the height of the second linear protrusion 108b (max). A line LC indicates the level of the center point of the second linear protrusion 108b (max).

  The line LA is located closer to the center of the electrode group 103 than the line La indicating the outermost level of the first portion 108A. At this time, the smaller the height difference (interval) Δh between the line La and the line LA, the larger the relative height of the second linear protrusion 108b, and the higher the stress relaxation effect.

  The ratio of the height hb of the second linear protrusion 108b (max) to the height ha of the first linear protrusion 108a (max): hb / ha should be larger than 1, but the effect of stress relaxation From the viewpoint of increasing the ratio, the hb / ha ratio preferably satisfies 1 <hb / ha ≦ 5, and more preferably satisfies 1 <hb / ha ≦ 10.

  The pitch (interval between adjacent first linear protrusions 108a) Pa of the first linear protrusions 108a is not particularly limited, but may be, for example, 0.5 to 3.0 mm. The pitch (interval between adjacent second linear protrusions 108b) Pb of the second linear protrusions 108b is not particularly limited, but may be, for example, 0.5 to 3.0 mm. Each pitch may not be constant. Pa may be obtained as an average value of pitches between all the adjacent first linear protrusions 108a. Pb may be obtained as an average value of pitches between all adjacent second linear convex portions 108b.

  For example, the first linear convex portion 108a and the second linear convex portion 108b are portions corresponding to the first portion 108A and the second portion 108B of the film material that is the material of the exterior body, and the first linear convex portion 108a. And / or it can form by pressing once or more with the metal mold | die which has a some ridgeline and a some valley line corresponding to the 2nd linear convex part 108b. Next, the envelope-shaped exterior body 108 is formed from a film material including the first portion 108A where the first linear protrusion 108a is formed and the second portion 108B where the second linear protrusion 108b is formed. . However, the formation method of the 1st linear convex part 108a and / or the 2nd linear convex part 108b is not limited to this.

  The step of accommodating the electrode group 103 in the outer package 108 in a state where the ends of the first lead 113 and the second lead 123 are led out from the opening of the outer package 108 and impregnating the electrode group 103 with a nonaqueous electrolyte under reduced pressure. Done. If the sealing material 130 is interposed between the opening end of the exterior body 108 and each lead and the sealing material 130 is heated under reduced pressure to seal the opening of the exterior body 108, a sealed thin battery can be obtained.

(Second Embodiment)
FIG. 4 is a longitudinal sectional view conceptually showing a main part of the thin battery 100X according to the second embodiment. The same elements as those in the first embodiment are denoted by the same reference numerals. The thin battery 100X according to this embodiment includes at least one spacer 131 between the second part 108B of the exterior body and the electrode group 103. The spacer 131 is a linear member having a shape corresponding to the second linear convex portion 108b or a member having a linear convex portion, and is disposed along the inside of the second linear convex portion 108b.

  The manufacturing process of the thin battery includes a step of impregnating the electrode group 103 with a nonaqueous electrolyte under reduced pressure, or heating the sealing material 130 under reduced pressure to seal the opening of the outer package 108. The exterior body 108 deforms along the shape of the spacer 131 during the operation under such reduced pressure. Thereby, the 2nd linear convex part 108b along the shape of the spacer 131 is formed. By using the spacer 131, it becomes easy to control the shape, number, height, and the like of the second linear protrusions 108b.

  The material of the spacer 131 is not particularly limited, but a thermoplastic resin having heat weldability is preferable. The spacer 131 formed of a thermoplastic resin having a heat welding property can be fixed to any part of the electrode group 103 or the tab by heat welding. Therefore, the spacer 131 can be prevented from moving from a desired position or falling off during manufacturing or when the battery is bent. Although it does not specifically limit as a thermoplastic resin, A polypropylene, an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer etc. can be used. In the illustrated example, the case where the spacer 131 is a plurality of linear members fixed to the assembly tab 124A is shown, but the present invention is not limited to this. For example, a plate member having a plurality of linear protrusions may be used as the spacer. Moreover, you may form only one 2nd linear convex part using only one linear member.

  In the second embodiment, the case where the spacer is accommodated in the battery has been described. However, for example, when the electrode group is impregnated with the non-aqueous electrolyte, or when the opening of the exterior body 108 is sealed, the operation is performed under reduced pressure. Inside, an external force may be applied to the second portion 108B of the exterior body 108 with a jig from the outside of the battery. As a result, the exterior body is deformed along the shape of the jig, and the deformation is maintained thereafter to form the second linear protrusion 108b. For example, since the exterior body 108 is loose before decompression, a part of the exterior body 108 can be sandwiched between two plate-shaped jigs from the outside of the battery. At this time, the exterior body 108 is deformed so that a linear wrinkle is formed in the second portion 108B. Thereafter, the work under reduced pressure is completed, and the deformation is maintained even after the reduced pressure is released, so that a bowl-shaped second linear protrusion 108b is formed.

(Third embodiment)
FIG. 5 is a longitudinal sectional view conceptually showing a main part of the thin battery 100Y according to the third embodiment. Here, the same (or corresponding) elements as those in the first embodiment are denoted by the same reference numerals. The thin battery 100 </ b> Y according to the present embodiment includes two first electrodes 110, one second electrode 120 interposed between the two first electrodes 110, and one outside each of the two first electrodes 110. And a second electrode 120 disposed. The first electrode 110 includes a first current collector sheet 111 and a first active material layer 112 attached to both surfaces. One second electrode 120 interposed between the two first electrodes 110 also includes a second current collector sheet 121 and a second active material layer 122 attached to both surfaces thereof. On the other hand, the second electrodes 120 arranged on the outermost sides are single-sided electrodes including the second current collector sheet 121 and the second active material layer 122 attached to one surface thereof.

  The first portion 108A of the outer package 108 of the thin battery 100Y is flat and does not have the first linear protrusion. Even in such a case, when the thin battery 100Y is bent, the width of the concave portion between the second linear convex portions 108b or the adjacent second linear convex portions 108b is enlarged or reduced. Cracks are unlikely to occur in the exterior body 108, and convex bulges are also unlikely to occur. The number of the second linear protrusions 108b is smaller than that of the thin battery 100 according to the first embodiment, but the second portion 108B is in contact with the electrode group 103 relatively gently. Demonstrate sufficient stress relaxation effect.

  However, the effect of stress relaxation increases as the height of the second linear protrusion 108b increases. Therefore, in FIG. 5, the difference in height (interval) Δh between the line LA indicating the level of the top of the highest second linear protrusion 108b (max) and the line La indicating the outermost level of the first part is small. Desirable. For example, Δh is desirably 50% or less of the height hb of the second linear protrusion 108b (max), and more desirably 0 to 30%.

Next, an electrode, a lead, a separator, a nonaqueous electrolyte, an exterior body, and the like constituting the electrode group will be described.
(Negative electrode)
The negative electrode has a negative electrode current collector sheet as the first or second current collector sheet and a negative electrode active material layer as the first or second active material layer. A metal film, metal foil, etc. are used for a negative electrode collector sheet. The material of the negative electrode current collector sheet is preferably at least one selected from the group consisting of copper, nickel, titanium and alloys thereof, and stainless steel. The thickness of the negative electrode current collector sheet is preferably 5 to 30 μm, for example.

  The negative electrode active material layer includes a negative electrode active material, and includes a binder and a conductive agent as necessary. The negative electrode active material layer may be a deposited film formed by a vapor phase method (for example, vapor deposition). Examples of the negative electrode active material include Li metal, a metal or alloy that electrochemically reacts with Li, a carbon material (for example, graphite), a silicon alloy, and a silicon oxide. The thickness of the negative electrode active material layer is preferably 1 to 300 μm, for example.

(Positive electrode)
The positive electrode has a positive electrode current collector sheet as a first or second current collector sheet and a positive electrode active material layer as a first or second active material layer. A metal film, a metal foil, or the like is used for the positive electrode current collector sheet. The material of the positive electrode current collector sheet is preferably at least one selected from the group consisting of, for example, silver, nickel, palladium, gold, platinum, aluminum, alloys thereof, and stainless steel. The thickness of the positive electrode current collector sheet is preferably 1 to 30 μm, for example.

The positive electrode active material layer includes a positive electrode active material and a binder, and includes a conductive agent as necessary. The positive electrode active material is not particularly limited. When the thin battery is a secondary battery, a lithium-containing composite oxide such as LiCoO ₂ or LiNiO ₂ is used. When the thin battery is a primary battery, manganese dioxide is used. Carbon fluoride (fluorinated graphite), lithium-containing composite oxide, and the like can be used. The thickness of the positive electrode active material layer is preferably 1 to 300 μm, for example.

  As the conductive agent included in the active material layer, graphite, carbon black, or the like is used. The amount of the conductive agent is, for example, 0 to 20 parts by mass per 100 parts by mass of the active material. As the binder to be included in the active material layer, fluorine resin, acrylic resin, rubber particles, or the like is used. The amount of the binder is, for example, 0.5 to 15 parts by mass per 100 parts by mass of the active material.

(Separator)
As the separator, a resin microporous film or a nonwoven fabric is preferably used. As the material (resin) for the separator, polyolefin (polyethylene, polypropylene, etc.), polyamide, polyamideimide, etc. are preferable. The thickness of the separator is, for example, 8 to 30 μm.

(Lead)
The negative electrode lead and the positive electrode lead are connected to the negative electrode current collector sheet or the positive electrode current collector sheet, respectively, by welding or the like. As the negative electrode lead, a copper lead, a copper alloy lead, a nickel lead, or the like is preferably used. As the positive electrode lead, a nickel lead, an aluminum lead or the like is preferably used.

(Nonaqueous electrolyte)
When the thin battery is a lithium ion battery, the nonaqueous electrolyte is preferably a mixture of a lithium salt and a nonaqueous solvent that dissolves the lithium salt. Examples of the lithium salt include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , and imide salts. Non-aqueous solvents include cyclic carbonates such as propylene carbonate, ethylene carbonate and butylene carbonate, chain carbonates such as diethyl carbonate, ethyl methyl carbonate and dimethyl carbonate, and cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone. Etc.

  It is preferable that at least a part of the nonaqueous electrolyte impregnated in the electrode group forms a gel electrolyte. The gel electrolyte is preferably present at least in the interface region between each active material layer and each separator. The presence of the gel electrolyte in the interface region between the active material layer and the separator improves the adhesion between the electrode and the separator. The gel electrolyte is preferably also present in the voids of each active material layer and / or in the pores of each separator.

  The gel electrolyte includes, for example, a non-aqueous electrolyte and a resin that swells with the non-aqueous electrolyte. As the resin that swells with the nonaqueous electrolyte, a fluororesin containing a vinylidene fluoride unit is preferable. A fluororesin containing a vinylidene fluoride unit tends to retain a nonaqueous electrolyte and easily gels.

  Examples of the fluororesin containing a vinylidene fluoride unit include polyvinylidene fluoride (PVdF), a copolymer (PVdF-HFP) containing a vinylidene fluoride (VdF) unit and a hexafluoropropylene (HFP) unit, and vinylidene fluoride (VdF). ) Units and trifluoroethylene (TFE) units. The amount of the vinylidene fluoride unit contained in the fluororesin containing the vinylidene fluoride unit is preferably 1 mol% or more so that the fluororesin can easily swell with the nonaqueous electrolyte.

When the gel electrolyte is disposed in the interface region between the active material layer and the separator, for example, a resin that swells with a nonaqueous electrolyte is applied to the surface of the active material layer and / or the surface of the separator, for example, in a thin film shape. Thereafter, the active material layer and the separator are laminated via a resin coating, and the obtained laminate or electrode group is impregnated with a nonaqueous electrolyte. As a result, the resin swells with the non-aqueous electrolyte, and a gel electrolyte is formed in the interface region. When a fluororesin containing a vinylidene fluoride unit is used for the gel electrolyte, the amount of the resin contained in the coating film is per unit surface area of the interface region between the active material layer and the separator (that is, per unit surface area of the active material layer or separator). 1 to 30 g / m ² is preferable.

  The exterior body is formed of, for example, a laminate film including a barrier layer against water vapor and resin layers respectively formed on both sides thereof. The material used for the barrier layer is not particularly limited, but it is preferable to use a metal layer, a ceramic layer, or the like. For example, metal materials such as aluminum, titanium, nickel, iron, platinum, gold, and silver, and ceramic materials such as silicon oxide, magnesium oxide, and aluminum oxide are preferable. The thickness of the barrier layer is preferably 0.01 to 50 μm, for example. The resin layer material disposed on the inner surface side of the outer package is made of polyolefin such as polyethylene and polypropylene, polyethylene terephthalate, polyamide, polyurethane, and polyethylene-acetic acid from the viewpoints of ease of thermal welding, electrolyte resistance, and chemical resistance. A vinyl copolymer (EVA) or the like is preferable. The thickness of the resin layer on the inner surface side is preferably 10 to 100 μm. The resin layer disposed on the outer surface side of the exterior body is made of polyamide such as 6,6-nylon, polyolefin, polyethylene terephthalate, polyester such as polybutylene terephthalate, etc. from the viewpoint of strength, impact resistance and chemical resistance. preferable. The thickness of the resin layer on the outer surface side is preferably 5 to 100 μm.

Example 1
In the following procedure, a thin battery having a pair of negative electrodes and a positive electrode sandwiched between them was produced.
(1) Production of negative electrode An electrolytic copper foil having a thickness of 8 μm was prepared as a negative electrode current collector sheet. The negative electrode mixture slurry was applied to one surface of the electrolytic copper foil, dried and rolled to form a negative electrode active material layer, thereby obtaining a negative electrode sheet. The negative electrode mixture slurry was prepared by mixing 100 parts by mass of graphite as a negative electrode active material, 8 parts by mass of polyvinylidene fluoride (PVdF) as a binder, and an appropriate amount of N-methyl-2-pyrrolidone (NMP). Prepared. The thickness of the negative electrode active material layer was 97 μm. A negative electrode having a size of 47.5 mm × 18 mm having a negative electrode tab of 5 mm × 5 mm was cut out from the negative electrode sheet, and the active material layer was peeled off from the negative electrode tab to expose the copper foil. Thereafter, a copper negative electrode lead was ultrasonically welded to the tip of the negative electrode tab of one negative electrode.

(2) Production of positive electrode An aluminum foil having a thickness of 15 μm was prepared as a positive electrode current collector sheet. The positive electrode mixture slurry was applied to both surfaces of the aluminum foil, dried and then rolled to form a positive electrode active material layer to obtain a positive electrode sheet. The positive electrode mixture slurry is a mixture of 100 parts by mass of lithium cobalt oxide as a positive electrode active material, 1.2 parts by mass of acetylene black as a conductive agent, 1.2 parts by mass of PVdF as a binder, and an appropriate amount of NMP. Prepared. The thickness (per one surface) of the positive electrode active material layer was 54 μm. A 45 mm × 16 mm positive electrode having a 5 mm × 5 mm tab was cut out from the positive electrode sheet, and the active material layer was peeled off from the positive electrode tab to expose the aluminum foil. Thereafter, an aluminum positive electrode lead was ultrasonically welded to the tip portion of the positive electrode tab.

(3) Nonaqueous electrolyte The nonaqueous electrolyte was prepared by dissolving LiPF ₆ in a mixed solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) as main components.

(4) Assembly of thin battery 5 parts by weight of PVdF was dissolved in 100 parts by weight of the mixed solvent to prepare a polymer solution. The obtained polymer solution was applied to both sides of a separator composed of a 49 mm × 18 mm microporous polyethylene film (thickness 9 μm), and then the solvent was stripped to form a PVdF film. The amount of PVdF applied was 15 g / m ² . Thereafter, the positive electrode was disposed between the pair of negative electrodes via a separator so that the negative electrode active material layer and the positive electrode active material layer faced each other, thereby forming an electrode group.

(5) Fabrication of exterior body and battery assembly As a material for the exterior body, a laminate film material (thickness: 73 μm) having an aluminum foil barrier layer, a polypropylene inner layer, and a nylon outer layer is used. Formed body. First, the laminate film material was cut into a rectangle of 29 mm × 120 mm and folded in half at the center in the longitudinal direction.

  Next, a plurality of striped first linear protrusions 108a parallel to the crease having a height (ha) of 100 μm and a pitch (Pa) of 0.9 mm are pressed into a portion corresponding to the first portion 108A of the laminate film material. Formed by processing.

  Next, five second linear protrusions 108b parallel to the crease having a height (hb) of 250 μm and a pitch (Pb) of 0.9 mm are formed by press working at a portion corresponding to the second portion 108B of the laminate film material. Formed.

  Next, the electrode group 103 is sandwiched between the two-fold laminate film material in which the first linear convex portion 108a and the second linear convex portion 108b are formed, and each lead of the electrode group 103 is led out from the opposite side of the fold. It was. Next, the joining margin of the two sides crossing the crease was welded, and the envelope-shaped exterior body 108 in a state where the electrode group 103 was accommodated was formed. Next, each lead portion overlapping the opening end of the envelope-shaped outer package 108 is surrounded by a sealing material (thermoplastic resin) 130, and then a non-aqueous electrolyte is injected from the opening, and the opening is opened under a reduced pressure of −650 mmHg. The end (sealing allowance) was thermally welded. Thereafter, the thin battery was aged in an environment of 45 ° C., and the entire electrode group was impregnated with a nonaqueous electrolyte. Finally, the battery was pressed at 25 ° C. at a pressure of 0.25 MPa for 30 seconds to produce a battery A1 having a thickness of 0.8 mm. In the battery A1, the top of the second linear protrusion 108b is located closer to the center than the outermost part of the first portion (the top of the first linear protrusion 108a), and the first in the thickness direction of the electrode group. The height difference (interval) Δh between the outermost part of the part (line La) and the top part (line LA) of the second linear protrusion 108b was 50 μm.

[Evaluation]
(Initial battery capacity)
Under the environment of 25 ° C., the battery A was charged and discharged as follows to determine the initial capacity (C ₀ ). However, the design capacity of the battery A1 is 1C (mAh).
(1) Constant current charging: 0.2 CmA (end voltage 4.2 V)
(2) Constant voltage charging: 4.35 V (end current 0.05 CmA)
(3) Constant current discharge: 0.5 CmA (end voltage 2.5 V)

(Capacity maintenance rate after bending test)
A pair of expandable and contractible fixing members were horizontally opposed to each other, and a battery A1 in a discharged state was attached to each fixing member and fixed. Then, in an environment of 25 ° C., the distance between both ends of the fixing member was shortened so that the curvature radius of the battery became R30 mm, and then both ends of the fixing member were returned to the original state to return the battery to a flat state. After repeating this operation 1000 times, the front and back of the battery were exchanged, and bending was performed 1000 times on the opposite surface of the battery.
Thereafter, the thin battery was charged and discharged under the same conditions as described above, and the discharge capacity (C _x ) after the bending test was obtained. From the obtained discharge capacity C _x and initial capacity C ₀ , the capacity retention rate was obtained from the following equation.
Capacity retention ratio after bending test (%) = (C _x / C ₀ ) × 100

  Ten batteries A1 were produced, and the same test was performed on each of them to determine the average value of the capacity retention rate. The results are shown in Table 1. In addition, the number of defective batteries in which cracks in the outer package or convex bulges (外 装) occurred in the stepped portion where the thickness of the electrode group changed was visually confirmed.

Example 2
Ten batteries A2 were produced and evaluated in the same manner as in Example 1 except that the first linear protrusion was not formed at the site corresponding to the first site 108A of the laminate film material. The results are shown in Table 1.

<< Comparative Example 1 >>
Ten batteries B1 were produced and evaluated in the same manner as in Example 1 except that the second linear protrusion was not formed in the portion corresponding to the second portion 108B of the laminate film material. The results are shown in Table 1.

  As shown in Table 1, in Examples 1 and 2, a high capacity retention rate was obtained and no defective battery was generated, whereas in Comparative Example 1, four defective batteries were generated. Also declined.

Example 3
A thin battery having three negative electrodes and two positive electrodes was produced by the following procedure.
(1) Production of negative electrode A single-sided negative electrode having a size of 47.5 mm x 18 mm having a negative electrode tab of 5 mm x 5 mm was produced in the same manner as in Example 1. Moreover, the double-sided negative electrode which has the negative electrode active material layer of 97 micrometers in thickness on both surfaces was produced with the same method using the negative electrode collector sheet and negative electrode mixture slurry similar to Example 1. Of the prepared three negative electrodes, a copper negative electrode lead was ultrasonically welded to the tip of one single-sided negative electrode tab.

(2) Production of positive electrode In the same manner as in Example 1, two positive electrodes were produced, and an aluminum positive electrode lead was ultrasonically welded to the tip portion of the positive electrode tab of one positive electrode.

(3) Assembly of thin battery A pair of single-sided negative electrodes were arranged in the outermost layer, and two positive electrodes and three negative electrodes were alternately stacked via a separator to form an electrode group.

(4) Production of exterior body and assembly of battery Using the same material as in Example 1, an envelope-shaped exterior body was formed in the following manner. First, the laminate film material was cut into a rectangle of 29 mm × 120 mm and folded in half at the center in the longitudinal direction.

  Next, a plurality of striped first linear protrusions 108a parallel to the folds having a height (ha) of 200 μm and a pitch (Pa) of 0.9 mm are pressed into a portion corresponding to the first portion 108A of the laminate film material. Formed by processing.

  Next, five second linear protrusions 108b parallel to the crease having a height (hb) of 500 μm and a pitch (Pb) of 0.9 mm are formed by press working at a portion corresponding to the second portion 108B of the laminate film material. Formed.

  Next, in the same manner as in Example 1, an envelope-shaped exterior body 108 in a state in which the electrode group 103 is accommodated is formed, each lead portion is surrounded by a sealing material 130, and then a nonaqueous electrolyte is injected from the opening. The open end (sealing margin) was thermally welded under a reduced pressure of -650 mmHg. Thereafter, the thin battery was aged in an environment of 45 ° C., and the entire electrode group was impregnated with a nonaqueous electrolyte. Finally, the battery was pressed at 25 ° C. for 30 seconds at a pressure of 0.25 MPa to produce a battery A3 having a thickness of 1.5 mm. In the battery A3, the top of the second linear protrusion 108b is located closer to the center than the outermost portion of the first portion (the top of the first linear protrusion 108a), and the first in the thickness direction of the electrode group. The height difference (interval) Δh between the outermost part of the part (line La) and the top part (line LA) of the second linear protrusion 108b was 100 μm. Battery A3 was evaluated in the same manner as described above. The results are shown in Table 2.

Example 4
Ten batteries A4 were produced and evaluated in the same manner as in Example 3 except that the first linear protrusion was not formed in the portion corresponding to the first portion 108A of the laminate film material. The results are shown in Table 2.

<< Comparative Example 2 >>
Ten batteries B2 were produced and evaluated in the same manner as in Example 3 except that the second linear protrusion was not formed in the portion corresponding to the second portion 108B of the laminate film material. The results are shown in Table 2.

  As shown in Table 2, in Examples 3 and 4, a high capacity retention rate was obtained and no defective battery was generated, whereas in Comparative Example 2, five defective batteries were generated, and therefore the capacity retention rate was Also declined.

  The thin battery of the present invention is suitable for use in a small electronic device such as a biological sticking device or a wearable portable terminal.

  100, 100X, 100Y: thin battery, 103: electrode group, 107: separator, 108: exterior body, 108A: first part, 108B: second part, 108a: first linear protrusion, 108b: second linear Convex part, 110: first electrode, 111: first current collector sheet, 112: first active material layer, 113: first lead, 114: first tab, 120: second electrode, 121: second current collector Body sheet, 122: second active material layer, 123: second lead, 124: second tab, 124A: assembly tab, 130: sealing material, 131: spacer

Claims (6)

A sheet-like electrode group, a non-aqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the non-aqueous electrolyte,
The electrode group includes:
A sheet-like first electrode;
A sheet-like second electrode;
A separator disposed between the first electrode and the second electrode;
Comprising
The first electrode includes a first current collector sheet and a first active material layer attached to the first current collector sheet,
The second electrode includes a second current collector sheet and a second active material layer attached to the second current collector sheet,
The first current collector sheet includes a first tab extending in a first direction from a part of one side of the first current collector sheet, and is drawn to the outside of the exterior body by the first tab. The lead is connected,
The second current collector sheet includes a second tab extending in a first direction from a part of one side of the second current collector sheet, and the second current collector sheet is pulled out of the exterior body by the second tab. 2 leads are connected,
The exterior body has a sealing margin for sandwiching the first lead and the second lead,
The exterior body includes a first part facing the first active material layer and the second active material layer, and a second part between the first part and the sealing allowance,
The first part has a flat surface or has a plurality of striped first linear protrusions intersecting the first direction,
The second portion has at least one second linear convex portion that intersects the first direction, and the height of the second linear convex portion is greater than the height of the first linear convex portion. battery.   2. The thin battery according to claim 1, wherein in the thickness direction of the electrode group, a center point of the height of the second linear protrusion is located closer to the center than the outermost part of the first part.   The thin battery according to claim 2, wherein in the thickness direction of the electrode group, a top portion of the second linear convex portion is located closer to the center than the outermost portion of the first portion.   The thin battery according to any one of claims 1 to 3, wherein the electrode group includes one first electrode and two second electrodes sandwiching the first electrode.   The electrode group includes two or more first electrodes and three or more second electrodes, and the first electrodes and the second electrodes are alternately stacked. 4. The thin battery according to any one of 3 above.   The thin battery according to any one of claims 1 to 5, wherein the thickness is 3 mm or less.

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